package com.smartandroid.sa.tag.nodes;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import com.smartandroid.sa.tag.helper.StringUtil;
import com.smartandroid.sa.tag.helper.Validate;
import com.smartandroid.sa.tag.parser.Parser;
import com.smartandroid.sa.tag.parser.Tag;
import com.smartandroid.sa.tag.select.Collector;
import com.smartandroid.sa.tag.select.Elements;
import com.smartandroid.sa.tag.select.Evaluator;
import com.smartandroid.sa.tag.select.NodeTraversor;
import com.smartandroid.sa.tag.select.NodeVisitor;
import com.smartandroid.sa.tag.select.Selector;

/**
 * A HTML element consists of a tag name, attributes, and child nodes (including
 * text nodes and other elements).
 * 
 * From an Element, you can extract data, traverse the node graph, and
 * manipulate the HTML.
 * 
 * @author Jonathan Hedley, jonathan@hedley.net
 */
public class Element extends Node {
	private Tag tag;
	private Set<String> classNames;

	/**
	 * Create a new, standalone Element. (Standalone in that is has no parent.)
	 * 
	 * @param tag
	 *            tag of this element
	 * @param baseUri
	 *            the base URI
	 * @param attributes
	 *            initial attributes
	 * @see #appendChild(Node)
	 * @see #appendElement(String)
	 */
	public Element(Tag tag, String baseUri, Attributes attributes) {
		super(baseUri, attributes);

		Validate.notNull(tag);
		this.tag = tag;
	}

	/**
	 * Create a new Element from a tag and a base URI.
	 * 
	 * @param tag
	 *            element tag
	 * @param baseUri
	 *            the base URI of this element. It is acceptable for the base
	 *            URI to be an empty string, but not null.
	 * @see Tag#valueOf(String)
	 */
	public Element(Tag tag, String baseUri) {
		this(tag, baseUri, new Attributes());
	}

	@Override
	public String nodeName() {
		return tag.getName();
	}

	/**
	 * Get the name of the tag for this element. E.g. {@code div}
	 * 
	 * @return the tag name
	 */
	public String tagName() {
		return tag.getName();
	}

	/**
	 * Change the tag of this element. For example, convert a {@code <span>} to
	 * a {@code <div>} with {@code el.tagName("div");}.
	 * 
	 * @param tagName
	 *            new tag name for this element
	 * @return this element, for chaining
	 */
	public Element tagName(String tagName) {
		Validate.notEmpty(tagName, "Tag name must not be empty.");
		tag = Tag.valueOf(tagName);
		return this;
	}

	/**
	 * Get the Tag for this element.
	 * 
	 * @return the tag object
	 */
	public Tag tag() {
		return tag;
	}

	/**
	 * Test if this element is a block-level element. (E.g.
	 * {@code <div> == true} or an inline element {@code <p> == false}).
	 * 
	 * @return true if block, false if not (and thus inline)
	 */
	public boolean isBlock() {
		return tag.isBlock();
	}

	/**
	 * Get the {@code id} attribute of this element.
	 * 
	 * @return The id attribute, if present, or an empty string if not.
	 */
	public String id() {
		String id = attr("id");
		return id == null ? "" : id;
	}

	/**
	 * Set an attribute value on this element. If this element already has an
	 * attribute with the key, its value is updated; otherwise, a new attribute
	 * is added.
	 * 
	 * @return this element
	 */
	public Element attr(String attributeKey, String attributeValue) {
		super.attr(attributeKey, attributeValue);
		return this;
	}

	/**
	 * Get this element's HTML5 custom data attributes. Each attribute in the
	 * element that has a key starting with "data-" is included the dataset.
	 * <p>
	 * E.g., the element
	 * {@code <div data-package="jsoup" data-language="Java" class="group">...}
	 * has the dataset {@code package=jsoup, language=java}.
	 * <p>
	 * This map is a filtered view of the element's attribute map. Changes to
	 * one map (add, remove, update) are reflected in the other map.
	 * <p>
	 * You can find elements that have data attributes using the
	 * {@code [^data-]} attribute key prefix selector.
	 * 
	 * @return a map of {@code key=value} custom data attributes.
	 */
	public Map<String, String> dataset() {
		return attributes.dataset();
	}

	@Override
	public final Element parent() {
		return (Element) parentNode;
	}

	/**
	 * Get this element's parent and ancestors, up to the document root.
	 * 
	 * @return this element's stack of parents, closest first.
	 */
	public Elements parents() {
		Elements parents = new Elements();
		accumulateParents(this, parents);
		return parents;
	}

	private static void accumulateParents(Element el, Elements parents) {
		Element parent = el.parent();
		if (parent != null && !parent.tagName().equals("#root")) {
			parents.add(parent);
			accumulateParents(parent, parents);
		}
	}

	/**
	 * Get a child element of this element, by its 0-based index number.
	 * <p/>
	 * Note that an element can have both mixed Nodes and Elements as children.
	 * This method inspects a filtered list of children that are elements, and
	 * the index is based on that filtered list.
	 * 
	 * @param index
	 *            the index number of the element to retrieve
	 * @return the child element, if it exists, otherwise throws an
	 *         {@code IndexOutOfBoundsException}
	 * @see #childNode(int)
	 */
	public Element child(int index) {
		return children().get(index);
	}

	/**
	 * Get this element's child elements.
	 * <p/>
	 * This is effectively a filter on {@link #childNodes()} to get Element
	 * nodes.
	 * 
	 * @return child elements. If this element has no children, returns an empty
	 *         list.
	 * @see #childNodes()
	 */
	public Elements children() {
		// create on the fly rather than maintaining two lists. if gets slow,
		// memoize, and mark dirty on change
		List<Element> elements = new ArrayList<Element>();
		for (Node node : childNodes) {
			if (node instanceof Element)
				elements.add((Element) node);
		}
		return new Elements(elements);
	}

	/**
	 * Get this element's child text nodes. The list is unmodifiable but the
	 * text nodes may be manipulated.
	 * <p/>
	 * This is effectively a filter on {@link #childNodes()} to get Text nodes.
	 * 
	 * @return child text nodes. If this element has no text nodes, returns an
	 *         empty list.
	 *         <p/>
	 *         For example, with the input HTML:
	 *         {@code <p>One <span>Two</span> Three <br> Four</p>} with the
	 *         {@code p} element selected:        <ul>
	 *         <li>{@code p.text()} = {@code "One Two Three Four"}</li>
	 *         <li>{@code p.ownText()} = {@code "One Three Four"}</li>
	 *         <li>{@code p.children()} = {@code Elements[<span>, <br>
	 * ]}</li>
	 *         <li>{@code p.childNodes()} = {@code List<Node>["One ", <span>, " Three ",
	 * <br>
	 * , " Four"]}</li>
	 *         <li>{@code p.textNodes()} =
	 *         {@code List<TextNode>["One ", " Three ", " Four"]}</li>
	 *         </ul>
	 */
	public List<TextNode> textNodes() {
		List<TextNode> textNodes = new ArrayList<TextNode>();
		for (Node node : childNodes) {
			if (node instanceof TextNode)
				textNodes.add((TextNode) node);
		}
		return Collections.unmodifiableList(textNodes);
	}

	/**
	 * Get this element's child data nodes. The list is unmodifiable but the
	 * data nodes may be manipulated.
	 * <p/>
	 * This is effectively a filter on {@link #childNodes()} to get Data nodes.
	 * 
	 * @return child data nodes. If this element has no data nodes, returns an
	 *         empty list.
	 * @see #data()
	 */
	public List<DataNode> dataNodes() {
		List<DataNode> dataNodes = new ArrayList<DataNode>();
		for (Node node : childNodes) {
			if (node instanceof DataNode)
				dataNodes.add((DataNode) node);
		}
		return Collections.unmodifiableList(dataNodes);
	}

	/**
	 * Find elements that match the {@link Selector} CSS query, with this
	 * element as the starting context. Matched elements may include this
	 * element, or any of its children.
	 * <p/>
	 * This method is generally more powerful to use than the DOM-type
	 * {@code getElementBy*} methods, because multiple filters can be combined,
	 * e.g.:
	 * <ul>
	 * <li>{@code el.select("a[href]")} - finds links ({@code a} tags with
	 * {@code href} attributes)
	 * <li>{@code el.select("a[href*=example.com]")} - finds links pointing to
	 * example.com (loosely)
	 * </ul>
	 * <p/>
	 * See the query syntax documentation in {@link org.jsoup.select.Selector}.
	 * 
	 * @param cssQuery
	 *            a {@link Selector} CSS-like query
	 * @return elements that match the query (empty if none match)
	 * @see org.jsoup.select.Selector
	 */
	public Elements select(String cssQuery) {
		return Selector.select(cssQuery, this);
	}

	/**
	 * Add a node child node to this element.
	 * 
	 * @param child
	 *            node to add.
	 * @return this element, so that you can add more child nodes or elements.
	 */
	public Element appendChild(Node child) {
		Validate.notNull(child);

		addChildren(child);
		return this;
	}

	/**
	 * Add a node to the start of this element's children.
	 * 
	 * @param child
	 *            node to add.
	 * @return this element, so that you can add more child nodes or elements.
	 */
	public Element prependChild(Node child) {
		Validate.notNull(child);

		addChildren(0, child);
		return this;
	}

	/**
	 * Inserts the given child nodes into this element at the specified index.
	 * Current nodes will be shifted to the right. The inserted nodes will be
	 * moved from their current parent. To prevent moving, copy the nodes first.
	 * 
	 * @param index
	 *            0-based index to insert children at. Specify {@code 0} to
	 *            insert at the start, {@code -1} at the end
	 * @param children
	 *            child nodes to insert
	 * @return this element, for chaining.
	 */
	public Element insertChildren(int index, Collection<? extends Node> children) {
		Validate.notNull(children,
				"Children collection to be inserted must not be null.");
		int currentSize = childNodeSize();
		if (index < 0)
			index += currentSize + 1; // roll around
		Validate.isTrue(index >= 0 && index <= currentSize,
				"Insert position out of bounds.");

		ArrayList<Node> nodes = new ArrayList<Node>(children);
		Node[] nodeArray = nodes.toArray(new Node[nodes.size()]);
		addChildren(index, nodeArray);
		return this;
	}

	/**
	 * Create a new element by tag name, and add it as the last child.
	 * 
	 * @param tagName
	 *            the name of the tag (e.g. {@code div}).
	 * @return the new element, to allow you to add content to it, e.g.:
	 *         {@code parent.appendElement("h1").attr("id", "header").text("Welcome");}
	 */
	public Element appendElement(String tagName) {
		Element child = new Element(Tag.valueOf(tagName), baseUri());
		appendChild(child);
		return child;
	}

	/**
	 * Create a new element by tag name, and add it as the first child.
	 * 
	 * @param tagName
	 *            the name of the tag (e.g. {@code div}).
	 * @return the new element, to allow you to add content to it, e.g.:
	 *         {@code parent.prependElement("h1").attr("id", "header").text("Welcome");}
	 */
	public Element prependElement(String tagName) {
		Element child = new Element(Tag.valueOf(tagName), baseUri());
		prependChild(child);
		return child;
	}

	/**
	 * Create and append a new TextNode to this element.
	 * 
	 * @param text
	 *            the unencoded text to add
	 * @return this element
	 */
	public Element appendText(String text) {
		TextNode node = new TextNode(text, baseUri());
		appendChild(node);
		return this;
	}

	/**
	 * Create and prepend a new TextNode to this element.
	 * 
	 * @param text
	 *            the unencoded text to add
	 * @return this element
	 */
	public Element prependText(String text) {
		TextNode node = new TextNode(text, baseUri());
		prependChild(node);
		return this;
	}

	/**
	 * Add inner HTML to this element. The supplied HTML will be parsed, and
	 * each node appended to the end of the children.
	 * 
	 * @param html
	 *            HTML to add inside this element, after the existing HTML
	 * @return this element
	 * @see #html(String)
	 */
	public Element append(String html) {
		Validate.notNull(html);

		List<Node> nodes = Parser.parseFragment(html, this, baseUri());
		addChildren(nodes.toArray(new Node[nodes.size()]));
		return this;
	}

	/**
	 * Add inner HTML into this element. The supplied HTML will be parsed, and
	 * each node prepended to the start of the element's children.
	 * 
	 * @param html
	 *            HTML to add inside this element, before the existing HTML
	 * @return this element
	 * @see #html(String)
	 */
	public Element prepend(String html) {
		Validate.notNull(html);

		List<Node> nodes = Parser.parseFragment(html, this, baseUri());
		addChildren(0, nodes.toArray(new Node[nodes.size()]));
		return this;
	}

	/**
	 * Insert the specified HTML into the DOM before this element (as a
	 * preceding sibling).
	 * 
	 * @param html
	 *            HTML to add before this element
	 * @return this element, for chaining
	 * @see #after(String)
	 */
	@Override
	public Element before(String html) {
		return (Element) super.before(html);
	}

	/**
	 * Insert the specified node into the DOM before this node (as a preceding
	 * sibling).
	 * 
	 * @param node
	 *            to add before this element
	 * @return this Element, for chaining
	 * @see #after(Node)
	 */
	@Override
	public Element before(Node node) {
		return (Element) super.before(node);
	}

	/**
	 * Insert the specified HTML into the DOM after this element (as a following
	 * sibling).
	 * 
	 * @param html
	 *            HTML to add after this element
	 * @return this element, for chaining
	 * @see #before(String)
	 */
	@Override
	public Element after(String html) {
		return (Element) super.after(html);
	}

	/**
	 * Insert the specified node into the DOM after this node (as a following
	 * sibling).
	 * 
	 * @param node
	 *            to add after this element
	 * @return this element, for chaining
	 * @see #before(Node)
	 */
	@Override
	public Element after(Node node) {
		return (Element) super.after(node);
	}

	/**
	 * Remove all of the element's child nodes. Any attributes are left as-is.
	 * 
	 * @return this element
	 */
	public Element empty() {
		childNodes.clear();
		return this;
	}

	/**
	 * Wrap the supplied HTML around this element.
	 * 
	 * @param html
	 *            HTML to wrap around this element, e.g.
	 *            {@code <div class="head"></div>}. Can be arbitrarily deep.
	 * @return this element, for chaining.
	 */
	@Override
	public Element wrap(String html) {
		return (Element) super.wrap(html);
	}

	/**
	 * Get sibling elements. If the element has no sibling elements, returns an
	 * empty list. An element is not a sibling of itself, so will not be
	 * included in the returned list.
	 * 
	 * @return sibling elements
	 */
	public Elements siblingElements() {
		if (parentNode == null)
			return new Elements(0);

		List<Element> elements = parent().children();
		Elements siblings = new Elements(elements.size() - 1);
		for (Element el : elements)
			if (el != this)
				siblings.add(el);
		return siblings;
	}

	/**
	 * Gets the next sibling element of this element. E.g., if a {@code div}
	 * contains two {@code p}s, the {@code nextElementSibling} of the first
	 * {@code p} is the second {@code p}.
	 * <p/>
	 * This is similar to {@link #nextSibling()}, but specifically finds only
	 * Elements
	 * 
	 * @return the next element, or null if there is no next element
	 * @see #previousElementSibling()
	 */
	public Element nextElementSibling() {
		if (parentNode == null)
			return null;
		List<Element> siblings = parent().children();
		Integer index = indexInList(this, siblings);
		Validate.notNull(index);
		if (siblings.size() > index + 1)
			return siblings.get(index + 1);
		else
			return null;
	}

	/**
	 * Gets the previous element sibling of this element.
	 * 
	 * @return the previous element, or null if there is no previous element
	 * @see #nextElementSibling()
	 */
	public Element previousElementSibling() {
		if (parentNode == null)
			return null;
		List<Element> siblings = parent().children();
		Integer index = indexInList(this, siblings);
		Validate.notNull(index);
		if (index > 0)
			return siblings.get(index - 1);
		else
			return null;
	}

	/**
	 * Gets the first element sibling of this element.
	 * 
	 * @return the first sibling that is an element (aka the parent's first
	 *         element child)
	 */
	public Element firstElementSibling() {
		// todo: should firstSibling() exclude this?
		List<Element> siblings = parent().children();
		return siblings.size() > 1 ? siblings.get(0) : null;
	}

	/**
	 * Get the list index of this element in its element sibling list. I.e. if
	 * this is the first element sibling, returns 0.
	 * 
	 * @return position in element sibling list
	 */
	public Integer elementSiblingIndex() {
		if (parent() == null)
			return 0;
		return indexInList(this, parent().children());
	}

	/**
	 * Gets the last element sibling of this element
	 * 
	 * @return the last sibling that is an element (aka the parent's last
	 *         element child)
	 */
	public Element lastElementSibling() {
		List<Element> siblings = parent().children();
		return siblings.size() > 1 ? siblings.get(siblings.size() - 1) : null;
	}

	private static <E extends Element> Integer indexInList(Element search,
			List<E> elements) {
		Validate.notNull(search);
		Validate.notNull(elements);

		for (int i = 0; i < elements.size(); i++) {
			E element = elements.get(i);
			if (element.equals(search))
				return i;
		}
		return null;
	}

	// DOM type methods

	/**
	 * Finds elements, including and recursively under this element, with the
	 * specified tag name.
	 * 
	 * @param tagName
	 *            The tag name to search for (case insensitively).
	 * @return a matching unmodifiable list of elements. Will be empty if this
	 *         element and none of its children match.
	 */
	public Elements getElementsByTag(String tagName) {
		Validate.notEmpty(tagName);
		tagName = tagName.toLowerCase().trim();

		return Collector.collect(new Evaluator.Tag(tagName), this);
	}

	/**
	 * Find an element by ID, including or under this element.
	 * <p>
	 * Note that this finds the first matching ID, starting with this element.
	 * If you search down from a different starting point, it is possible to
	 * find a different element by ID. For unique element by ID within a
	 * Document, use {@link Document#getElementById(String)}
	 * 
	 * @param id
	 *            The ID to search for.
	 * @return The first matching element by ID, starting with this element, or
	 *         null if none found.
	 */
	public Element getElementById(String id) {
		Validate.notEmpty(id);

		Elements elements = Collector.collect(new Evaluator.Id(id), this);
		if (elements.size() > 0)
			return elements.get(0);
		else
			return null;
	}

	/**
	 * Find elements that have this class, including or under this element. Case
	 * insensitive.
	 * <p>
	 * Elements can have multiple classes (e.g.
	 * {@code <div class="header round first">}. This method checks each class,
	 * so you can find the above with {@code el.getElementsByClass("header");}.
	 * 
	 * @param className
	 *            the name of the class to search for.
	 * @return elements with the supplied class name, empty if none
	 * @see #hasClass(String)
	 * @see #classNames()
	 */
	public Elements getElementsByClass(String className) {
		Validate.notEmpty(className);

		return Collector.collect(new Evaluator.Class(className), this);
	}

	/**
	 * Find elements that have a named attribute set. Case insensitive.
	 * 
	 * @param key
	 *            name of the attribute, e.g. {@code href}
	 * @return elements that have this attribute, empty if none
	 */
	public Elements getElementsByAttribute(String key) {
		Validate.notEmpty(key);
		key = key.trim().toLowerCase();

		return Collector.collect(new Evaluator.Attribute(key), this);
	}

	/**
	 * Find elements that have an attribute name starting with the supplied
	 * prefix. Use {@code data-} to find elements that have HTML5 datasets.
	 * 
	 * @param keyPrefix
	 *            name prefix of the attribute e.g. {@code data-}
	 * @return elements that have attribute names that start with with the
	 *         prefix, empty if none.
	 */
	public Elements getElementsByAttributeStarting(String keyPrefix) {
		Validate.notEmpty(keyPrefix);
		keyPrefix = keyPrefix.trim().toLowerCase();

		return Collector.collect(new Evaluator.AttributeStarting(keyPrefix),
				this);
	}

	/**
	 * Find elements that have an attribute with the specific value. Case
	 * insensitive.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param value
	 *            value of the attribute
	 * @return elements that have this attribute with this value, empty if none
	 */
	public Elements getElementsByAttributeValue(String key, String value) {
		return Collector.collect(new Evaluator.AttributeWithValue(key, value),
				this);
	}

	/**
	 * Find elements that either do not have this attribute, or have it with a
	 * different value. Case insensitive.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param value
	 *            value of the attribute
	 * @return elements that do not have a matching attribute
	 */
	public Elements getElementsByAttributeValueNot(String key, String value) {
		return Collector.collect(
				new Evaluator.AttributeWithValueNot(key, value), this);
	}

	/**
	 * Find elements that have attributes that start with the value prefix. Case
	 * insensitive.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param valuePrefix
	 *            start of attribute value
	 * @return elements that have attributes that start with the value prefix
	 */
	public Elements getElementsByAttributeValueStarting(String key,
			String valuePrefix) {
		return Collector.collect(new Evaluator.AttributeWithValueStarting(key,
				valuePrefix), this);
	}

	/**
	 * Find elements that have attributes that end with the value suffix. Case
	 * insensitive.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param valueSuffix
	 *            end of the attribute value
	 * @return elements that have attributes that end with the value suffix
	 */
	public Elements getElementsByAttributeValueEnding(String key,
			String valueSuffix) {
		return Collector.collect(new Evaluator.AttributeWithValueEnding(key,
				valueSuffix), this);
	}

	/**
	 * Find elements that have attributes whose value contains the match string.
	 * Case insensitive.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param match
	 *            substring of value to search for
	 * @return elements that have attributes containing this text
	 */
	public Elements getElementsByAttributeValueContaining(String key,
			String match) {
		return Collector.collect(new Evaluator.AttributeWithValueContaining(
				key, match), this);
	}

	/**
	 * Find elements that have attributes whose values match the supplied
	 * regular expression.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param pattern
	 *            compiled regular expression to match against attribute values
	 * @return elements that have attributes matching this regular expression
	 */
	public Elements getElementsByAttributeValueMatching(String key,
			Pattern pattern) {
		return Collector.collect(new Evaluator.AttributeWithValueMatching(key,
				pattern), this);

	}

	/**
	 * Find elements that have attributes whose values match the supplied
	 * regular expression.
	 * 
	 * @param key
	 *            name of the attribute
	 * @param regex
	 *            regular expression to match against attribute values. You can
	 *            use <a href=
	 *            "http://java.sun.com/docs/books/tutorial/essential/regex/pattern.html#embedded"
	 *            >embedded flags</a> (such as (?i) and (?m) to control regex
	 *            options.
	 * @return elements that have attributes matching this regular expression
	 */
	public Elements getElementsByAttributeValueMatching(String key, String regex) {
		Pattern pattern;
		try {
			pattern = Pattern.compile(regex);
		} catch (PatternSyntaxException e) {
			throw new IllegalArgumentException(
					"Pattern syntax error: " + regex, e);
		}
		return getElementsByAttributeValueMatching(key, pattern);
	}

	/**
	 * Find elements whose sibling index is less than the supplied index.
	 * 
	 * @param index
	 *            0-based index
	 * @return elements less than index
	 */
	public Elements getElementsByIndexLessThan(int index) {
		return Collector.collect(new Evaluator.IndexLessThan(index), this);
	}

	/**
	 * Find elements whose sibling index is greater than the supplied index.
	 * 
	 * @param index
	 *            0-based index
	 * @return elements greater than index
	 */
	public Elements getElementsByIndexGreaterThan(int index) {
		return Collector.collect(new Evaluator.IndexGreaterThan(index), this);
	}

	/**
	 * Find elements whose sibling index is equal to the supplied index.
	 * 
	 * @param index
	 *            0-based index
	 * @return elements equal to index
	 */
	public Elements getElementsByIndexEquals(int index) {
		return Collector.collect(new Evaluator.IndexEquals(index), this);
	}

	/**
	 * Find elements that contain the specified string. The search is case
	 * insensitive. The text may appear directly in the element, or in any of
	 * its descendants.
	 * 
	 * @param searchText
	 *            to look for in the element's text
	 * @return elements that contain the string, case insensitive.
	 * @see Element#text()
	 */
	public Elements getElementsContainingText(String searchText) {
		return Collector.collect(new Evaluator.ContainsText(searchText), this);
	}

	/**
	 * Find elements that directly contain the specified string. The search is
	 * case insensitive. The text must appear directly in the element, not in
	 * any of its descendants.
	 * 
	 * @param searchText
	 *            to look for in the element's own text
	 * @return elements that contain the string, case insensitive.
	 * @see Element#ownText()
	 */
	public Elements getElementsContainingOwnText(String searchText) {
		return Collector.collect(new Evaluator.ContainsOwnText(searchText),
				this);
	}

	/**
	 * Find elements whose text matches the supplied regular expression.
	 * 
	 * @param pattern
	 *            regular expression to match text against
	 * @return elements matching the supplied regular expression.
	 * @see Element#text()
	 */
	public Elements getElementsMatchingText(Pattern pattern) {
		return Collector.collect(new Evaluator.Matches(pattern), this);
	}

	/**
	 * Find elements whose text matches the supplied regular expression.
	 * 
	 * @param regex
	 *            regular expression to match text against. You can use <a href=
	 *            "http://java.sun.com/docs/books/tutorial/essential/regex/pattern.html#embedded"
	 *            >embedded flags</a> (such as (?i) and (?m) to control regex
	 *            options.
	 * @return elements matching the supplied regular expression.
	 * @see Element#text()
	 */
	public Elements getElementsMatchingText(String regex) {
		Pattern pattern;
		try {
			pattern = Pattern.compile(regex);
		} catch (PatternSyntaxException e) {
			throw new IllegalArgumentException(
					"Pattern syntax error: " + regex, e);
		}
		return getElementsMatchingText(pattern);
	}

	/**
	 * Find elements whose own text matches the supplied regular expression.
	 * 
	 * @param pattern
	 *            regular expression to match text against
	 * @return elements matching the supplied regular expression.
	 * @see Element#ownText()
	 */
	public Elements getElementsMatchingOwnText(Pattern pattern) {
		return Collector.collect(new Evaluator.MatchesOwn(pattern), this);
	}

	/**
	 * Find elements whose text matches the supplied regular expression.
	 * 
	 * @param regex
	 *            regular expression to match text against. You can use <a href=
	 *            "http://java.sun.com/docs/books/tutorial/essential/regex/pattern.html#embedded"
	 *            >embedded flags</a> (such as (?i) and (?m) to control regex
	 *            options.
	 * @return elements matching the supplied regular expression.
	 * @see Element#ownText()
	 */
	public Elements getElementsMatchingOwnText(String regex) {
		Pattern pattern;
		try {
			pattern = Pattern.compile(regex);
		} catch (PatternSyntaxException e) {
			throw new IllegalArgumentException(
					"Pattern syntax error: " + regex, e);
		}
		return getElementsMatchingOwnText(pattern);
	}

	/**
	 * Find all elements under this element (including self, and children of
	 * children).
	 * 
	 * @return all elements
	 */
	public Elements getAllElements() {
		return Collector.collect(new Evaluator.AllElements(), this);
	}

	/**
	 * Gets the combined text of this element and all its children.
	 * <p>
	 * For example, given HTML {@code <p>Hello <b>there</b> now!</p>},
	 * {@code p.text()} returns {@code "Hello there now!"}
	 * 
	 * @return unencoded text, or empty string if none.
	 * @see #ownText()
	 * @see #textNodes()
	 */
	public String text() {
		final StringBuilder accum = new StringBuilder();
		new NodeTraversor(new NodeVisitor() {
			public void head(Node node, int depth) {
				if (node instanceof TextNode) {
					TextNode textNode = (TextNode) node;
					appendNormalisedText(accum, textNode);
				} else if (node instanceof Element) {
					Element element = (Element) node;
					if (accum.length() > 0
							&& (element.isBlock() || element.tag.getName()
									.equals("br"))
							&& !TextNode.lastCharIsWhitespace(accum))
						accum.append(" ");
				}
			}

			public void tail(Node node, int depth) {
			}
		}).traverse(this);
		return accum.toString().trim();
	}

	/**
	 * Gets the text owned by this element only; does not get the combined text
	 * of all children.
	 * <p>
	 * For example, given HTML {@code <p>Hello <b>there</b> now!</p>},
	 * {@code p.ownText()} returns {@code "Hello now!"}, whereas
	 * {@code p.text()} returns {@code "Hello there now!"}. Note that the text
	 * within the {@code b} element is not returned, as it is not a direct child
	 * of the {@code p} element.
	 * 
	 * @return unencoded text, or empty string if none.
	 * @see #text()
	 * @see #textNodes()
	 */
	public String ownText() {
		StringBuilder sb = new StringBuilder();
		ownText(sb);
		return sb.toString().trim();
	}

	private void ownText(StringBuilder accum) {
		for (Node child : childNodes) {
			if (child instanceof TextNode) {
				TextNode textNode = (TextNode) child;
				appendNormalisedText(accum, textNode);
			} else if (child instanceof Element) {
				appendWhitespaceIfBr((Element) child, accum);
			}
		}
	}

	private static void appendNormalisedText(StringBuilder accum,
			TextNode textNode) {
		String text = textNode.getWholeText();

		if (preserveWhitespace(textNode.parentNode))
			accum.append(text);
		else
			StringUtil.appendNormalisedWhitespace(accum, text,
					TextNode.lastCharIsWhitespace(accum));
	}

	private static void appendWhitespaceIfBr(Element element,
			StringBuilder accum) {
		if (element.tag.getName().equals("br")
				&& !TextNode.lastCharIsWhitespace(accum))
			accum.append(" ");
	}

	static boolean preserveWhitespace(Node node) {
		// looks only at this element and one level up, to prevent recursion &
		// needless stack searches
		if (node != null && node instanceof Element) {
			Element element = (Element) node;
			return element.tag.preserveWhitespace() || element.parent() != null
					&& element.parent().tag.preserveWhitespace();
		}
		return false;
	}

	/**
	 * Set the text of this element. Any existing contents (text or elements)
	 * will be cleared
	 * 
	 * @param text
	 *            unencoded text
	 * @return this element
	 */
	public Element text(String text) {
		Validate.notNull(text);

		empty();
		TextNode textNode = new TextNode(text, baseUri);
		appendChild(textNode);

		return this;
	}

	/**
	 * Test if this element has any text content (that is not just whitespace).
	 * 
	 * @return true if element has non-blank text content.
	 */
	public boolean hasText() {
		for (Node child : childNodes) {
			if (child instanceof TextNode) {
				TextNode textNode = (TextNode) child;
				if (!textNode.isBlank())
					return true;
			} else if (child instanceof Element) {
				Element el = (Element) child;
				if (el.hasText())
					return true;
			}
		}
		return false;
	}

	/**
	 * Get the combined data of this element. Data is e.g. the inside of a
	 * {@code script} tag.
	 * 
	 * @return the data, or empty string if none
	 * 
	 * @see #dataNodes()
	 */
	public String data() {
		StringBuilder sb = new StringBuilder();

		for (Node childNode : childNodes) {
			if (childNode instanceof DataNode) {
				DataNode data = (DataNode) childNode;
				sb.append(data.getWholeData());
			} else if (childNode instanceof Element) {
				Element element = (Element) childNode;
				String elementData = element.data();
				sb.append(elementData);
			}
		}
		return sb.toString();
	}

	/**
	 * Gets the literal value of this element's "class" attribute, which may
	 * include multiple class names, space separated. (E.g. on
	 * <code>&lt;div class="header gray"></code> returns, "
	 * <code>header gray</code>")
	 * 
	 * @return The literal class attribute, or <b>empty string</b> if no class
	 *         attribute set.
	 */
	public String className() {
		return attr("class");
	}

	/**
	 * Get all of the element's class names. E.g. on element
	 * {@code <div class="header gray"}>}, returns a set of two elements
	 * {@code "header", "gray"}. Note that modifications to this set are not
	 * pushed to the backing {@code class} attribute; use the
	 * {@link #classNames(java.util.Set)} method to persist them.
	 * 
	 * @return set of classnames, empty if no class attribute
	 */
	public Set<String> classNames() {
		if (classNames == null) {
			String[] names = className().split("\\s+");
			classNames = new LinkedHashSet<String>(Arrays.asList(names));
		}
		return classNames;
	}

	/**
	 * Set the element's {@code class} attribute to the supplied class names.
	 * 
	 * @param classNames
	 *            set of classes
	 * @return this element, for chaining
	 */
	public Element classNames(Set<String> classNames) {
		Validate.notNull(classNames);
		attributes.put("class", StringUtil.join(classNames, " "));
		return this;
	}

	/**
	 * Tests if this element has a class. Case insensitive.
	 * 
	 * @param className
	 *            name of class to check for
	 * @return true if it does, false if not
	 */
	public boolean hasClass(String className) {
		Set<String> classNames = classNames();
		for (String name : classNames) {
			if (className.equalsIgnoreCase(name))
				return true;
		}
		return false;
	}

	/**
	 * Add a class name to this element's {@code class} attribute.
	 * 
	 * @param className
	 *            class name to add
	 * @return this element
	 */
	public Element addClass(String className) {
		Validate.notNull(className);

		Set<String> classes = classNames();
		classes.add(className);
		classNames(classes);

		return this;
	}

	/**
	 * Remove a class name from this element's {@code class} attribute.
	 * 
	 * @param className
	 *            class name to remove
	 * @return this element
	 */
	public Element removeClass(String className) {
		Validate.notNull(className);

		Set<String> classes = classNames();
		classes.remove(className);
		classNames(classes);

		return this;
	}

	/**
	 * Toggle a class name on this element's {@code class} attribute: if
	 * present, remove it; otherwise add it.
	 * 
	 * @param className
	 *            class name to toggle
	 * @return this element
	 */
	public Element toggleClass(String className) {
		Validate.notNull(className);

		Set<String> classes = classNames();
		if (classes.contains(className))
			classes.remove(className);
		else
			classes.add(className);
		classNames(classes);

		return this;
	}

	/**
	 * Get the value of a form element (input, textarea, etc).
	 * 
	 * @return the value of the form element, or empty string if not set.
	 */
	public String val() {
		if (tagName().equals("textarea"))
			return text();
		else
			return attr("value");
	}

	/**
	 * Set the value of a form element (input, textarea, etc).
	 * 
	 * @param value
	 *            value to set
	 * @return this element (for chaining)
	 */
	public Element val(String value) {
		if (tagName().equals("textarea"))
			text(value);
		else
			attr("value", value);
		return this;
	}

	void outerHtmlHead(StringBuilder accum, int depth,
			Document.OutputSettings out) {
		if (accum.length() > 0
				&& out.prettyPrint()
				&& (tag.formatAsBlock()
						|| (parent() != null && parent().tag().formatAsBlock()) || out
							.outline()))
			indent(accum, depth, out);
		accum.append("<").append(tagName());
		attributes.html(accum, out);

		// selfclosing includes unknown tags, isEmpty defines tags that are
		// always empty
		if (childNodes.isEmpty() && tag.isSelfClosing()) {
			if (out.syntax() == Document.OutputSettings.Syntax.html
					&& tag.isEmpty())
				accum.append('>');
			else
				accum.append(" />"); // <img> in html, <img /> in xml
		} else
			accum.append(">");
	}

	void outerHtmlTail(StringBuilder accum, int depth,
			Document.OutputSettings out) {
		if (!(childNodes.isEmpty() && tag.isSelfClosing())) {
			if (out.prettyPrint()
					&& (!childNodes.isEmpty() && (tag.formatAsBlock() || (out
							.outline() && (childNodes.size() > 1 || (childNodes
							.size() == 1 && !(childNodes.get(0) instanceof TextNode)))))))
				indent(accum, depth, out);
			accum.append("</").append(tagName()).append(">");
		}
	}

	/**
	 * Retrieves the element's inner HTML. E.g. on a {@code <div>} with one
	 * empty {@code <p>}, would return {@code <p></p>}. (Whereas
	 * {@link #outerHtml()} would return {@code <div>
	 * <p></p>
	 * </div>}.)
	 * 
	 * @return String of HTML.
	 * @see #outerHtml()
	 */
	public String html() {
		StringBuilder accum = new StringBuilder();
		html(accum);
		return getOutputSettings().prettyPrint() ? accum.toString().trim()
				: accum.toString();
	}

	private void html(StringBuilder accum) {
		for (Node node : childNodes)
			node.outerHtml(accum);
	}

	/**
	 * Set this element's inner HTML. Clears the existing HTML first.
	 * 
	 * @param html
	 *            HTML to parse and set into this element
	 * @return this element
	 * @see #append(String)
	 */
	public Element html(String html) {
		empty();
		append(html);
		return this;
	}

	public String toString() {
		return outerHtml();
	}

	@Override
	public boolean equals(Object o) {
		return this == o;
	}

	@Override
	public int hashCode() {
		// todo: fixup, not very useful
		int result = super.hashCode();
		result = 31 * result + (tag != null ? tag.hashCode() : 0);
		return result;
	}

	@Override
	public Element clone() {
		Element clone = (Element) super.clone();
		clone.classNames = null; // derived on first hit, otherwise gets a
									// pointer to source classnames
		return clone;
	}
}
